Document Type

Article

Publication Date

8-16-2011

Publication Title

Proceedings of the National Academy of Sciences of the United States of America

Department

Thayer School of Engineering

Abstract

Clostridium thermocellum is a thermophilic, obligately anaerobic, Gram-positive bacterium that is a candidate microorganism for converting cellulosic biomass into ethanol through consolidated bioprocessing. Ethanol intolerance is an important metric in terms of process economics, and tolerance has often been described as a complex and likely multigenic trait for which complex gene interactions come into play. Here, we resequence the genome of an ethanol-tolerant mutant, show that the tolerant phenotype is primarily due to a mutated bifunctional acetaldehyde-CoA/alcohol dehydrogenase gene (adhE), hypothesize based on structural analysis that cofactor specificity may be affected, and confirm this hypothesis using enzyme assays. Biochemical assays confirm a complete loss of NADH-dependent activity with concomitant acquisition of NADPH-dependent activity, which likely affects electron flow in the mutant. The simplicity of the genetic basis for the ethanol-tolerant phenotype observed here informs rational engineering of mutant microbial strains for cellulosic ethanol production.

DOI

10.1073/pnas.1102444108

Original Citation

Brown SD, Guss AM, Karpinets TV, Parks JM, Smolin N, Yang S, Land ML, Klingeman DM, Bhandiwad A, Rodriguez M Jr, Raman B, Shao X, Mielenz JR, Smith JC, Keller M, Lynd LR. Mutant alcohol dehydrogenase leads to improved ethanol tolerance in Clostridium thermocellum. Proc Natl Acad Sci U S A. 2011 Aug 16;108(33):13752-7. doi: 10.1073/pnas.1102444108. Epub 2011 Aug 8. PMID: 21825121; PMCID: PMC3158198.

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